Answer
The sum of first 10 terms = 5115
Work Step by Step
Given sequence = 5, 10, 20, 40......
This is a geometric sequence
first term $a_{1}$ = 5
Common ratio (r) = $\frac{40}{20}$ = 2
The sum of first n terms = $a_{1}\frac{1 - r^{n}}{1 - r}$
The sum of first 10 terms = 5 $\frac{1 - 2^{10}}{1 - 2}$
= 5115
